allow syntax of units (m)^2

package.json

@@ -4,7 +4,7 @@
  "description": "Programming platform for Quantitative Systems Pharmacology modeling in NodeJS",
  "main": "src/index.js",
  "scripts": {
- "test:dev": "mocha test/check-units/calc-unit --config=./test/.mocharc.json",
+ "test:dev": "mocha test/unit/parse-and-stringify --config=./test/.mocharc.json",
  "test": "mocha test --config=./test/.mocharc.json",
  "jsdoc": "jsdoc -r -c .jsdoc.json --readme api-references.md -d docs/dev src",
  "test:cov": "nyc --reporter=lcov npm run test",

src/core/unit.js

@@ -233,7 +233,7 @@ class Unit extends Array {
  * @param {String} unitString - string of format 'mM^2*L/mg/h2' or (1e-2 mg)^3/L
  * @return {Unit} A Unit object.
  */
- static parse(unitString){
+ static parse(unitString) {
  let unit = new Unit();
 
  // create string from number
@@ -250,7 +250,7 @@ class Unit extends Array {
  // checking "/xxx^12.23" or "1" or "/1"
  let shortFormat = /^(\/|\*)?[_A-Za-z1][_A-Za-z0-9]*\^?(\d+(\.?\d*)?)?$/;
  // checking "/(1e-2xxx)^12.23"
- let longFormat = /^(\/|\*)?\(\d+(\.\d*)?([eE][+-]?\d+)?([_A-Za-z][_A-Za-z0-9]*)?\)\^?(\d+(\.?\d*)?)?$/;
+ let longFormat = /^(\/|\*)?\((\d+(\.\d*)?)?([eE][+-]?\d+)?([_A-Za-z][_A-Za-z0-9]*)?\)\^?(\d+(\.?\d*)?)?$/;
 
  if (!shortFormat.test(item) && !longFormat.test(item)) 
  throw new SyntaxError(`Wrong syntax of unit's item: "${unitString}"`);

test/unit/parse-and-stringify.js

@@ -26,6 +26,8 @@ const correctUnits = [
  {str0: 'xxx_yyy', str: 'xxx_yyy', hash: '_xxx_yyy', tex: 'xxx\\_yyy', html: 'xxx_yyy'},
  {str0: 'xxx_yyy*aaa_bbb^2', str: 'xxx_yyy*aaa_bbb^2', hash: '_xxx_yyy_aaa_bbb2', tex: 'xxx\\_yyy \\cdot aaa\\_bbb^{2}', html: 'xxx_yyy&times;aaa_bbb<sup>2</sup>'},
  {str0: 'u12x', str: 'u12x', hash: '_u12x', tex: 'u12x', html: 'u12x'},
+ {str0: '(L)', str: 'L', hash: '_L', tex: 'L', html: 'L'},
+ {str0: '(metre)^2', str: 'metre^2', hash: '_metre2', tex: 'metre^{2}', html: 'metre<sup>2</sup>'},
 ];
 
 describe('Testing correct units.', () => {